The present invention is directed to a device for clamping and/or tensioning. More specifically, the present invention is specifically directed to a device for clamping or tensioning a plate or a packing on a cylinder.
DE 195 09 561 C2 discloses a device for clamping plates, which has a swiveling spindle. The plates are frictionally held between a channel wall and pressure cams that are arranged radially in the spindle. Clamping is performed by turning the swiveling spindle until the cams act almost normally on the plates resting against the channel wall. In a similar manner, DE 40 05 093 C1 shows an eccentrically seated spindle, which frictionally clamps the plates between its surface shell and the channel wall when the spindle is turned.
A device for actuating a tensioning device is known from DE 34 01 760 A1, in which the tensioning spindle is structured as a profiled shaft. Tensioning takes place by turning the head of the tensioning spindle, which projects past the end face of the cylinder, and which displaces a tensioning strip in the circumferential direction. The spindle is non-positively secured against an automatic return movement by pressing the surface of a pin of the spindle into a bracket.
U.S. Pat. No. 4,495,865 shows a device for accomplishing the positive arresting of a device for tensioning packings on cylinders by turning a spindle. A crown gear is assigned to one of the ends of the spindle. Arresting is performed by the use of a blade, which is placed nearly tangentially against the crown gear. The shape of the teeth and the arrangement of the blade have been selected in such a way that turning of the spindle in the tensioning direction is possible, but a return movement is prevented. To release the device, the blade is pivoted away from the crown gear by actuating a lever that is assigned to the blade.
DE 44 42 300 A1 also shows a device for tensioning packings, that has an arresting device which, in the operating state, permits turning of the tensioning device in the tensioning direction, but blocks a return movement. Tensioning and arresting, or releasing, here takes place by the use of a single actuating device that is arranged in an extension of the spindle and which is turned for tensioning the packing in the circumferential direction of the spindle, and for arresting/releasing the spindle is moved axially in respect to the spindle axis. No limitation of the travel or force in the tensioning direction is provided.
DE 29 10 880 C2 also discloses a device for tensioning a packing, wherein the tensioning of a packing and the arresting of a shaft takes place by the use of a single device. Tensioning and arresting by the utilization of the friction of a threaded bolt arranged in a screw thread takes place by the same movement.
A device for clamping/tensioning a packing and for arresting the device is known from U.S. Pat. No. 4,417,517. Tensioning is performed by the use of swiveling a shaft, and arresting is accomplished by the use of a lever which must be specifically actuated.
The object of the present invention is directed to providing a device for clamping and/or tensioning.
In accordance with the present invention, this object is attained by providing a packing clamping or tensioning device in which packing clamping and tensioning, as well as the arresting of a shaft with respect to its axis of rotation, can be performed by a single device. For clamping and tensioning, this single device can be rotated about an axis that is parallel with the rotational axis of the shaft. For arresting movement of the shaft, the device is pivotable about a pivot axis that is perpendicular to the axis of rotation of the shaft.
An advantage to be achieved by the present invention resides, in particular, in that one single device permits both clamping, or tensioning of packings and, at the same time, the positive arresting in the desired position of the clamping device. An actuation of separately provided devices for arresting, or releasing, and for clamping, or tensioning, is not required. The device for clamping or tensioning, in accordance with the present invention, is simple to operate and can be accurately and dependably arrested in respect to available locking mechanisms.
A further advantage of the device of the present invention is that arresting is provided by the provision of a positive connection, wherein the effective surfaces take place nearly perpendicularly to the circumferential surface and therefore normal in respect to the possible movement or force direction of the shaft or spindle. Release of the subject device, in response to centrifugal forces, or to fluctuations or micro-movements, as is possible with the use of non-positive connections or with the use of resilient lever mechanisms, cannot occur.
Arresting can be performed in a simple self-locking manner. In the operating state of the cylinder, i.e. in the state of rest of the device for clamping and/or tensioning, the device is maintained positively arrested.
The arrangement of the present invention, with the arresting device acting positively in both directions of rotation of the spindle, is particularly advantageous. This permits an exact, reproducible positioning of the shaft or spindle, and thus of the surfaces working together with the packing, and further permits a defined position, independently of pretensioning of the device or the packing. The position of the spindle is important, in particular, for non-positive or for positive holding or tensioning with the aid of profiled shafts, cams or gripping members on shafts. A small positional change of the surface in the circumferential direction, which works together with the packing, or an initially not quite exactly set position might cause the xe2x80x9copeningxe2x80x9d of the device, in particular, if the operation is performed at dead center (unstable equilibrium). By arresting the spindle in both adjustment directions, the unintentional displacement of the spindle by forces or movements which are oriented out of the channel, as well as forces or movements directed into the channel, is prevented. The former are caused, for example, by the pulling force of the packing or by a centrifugal force. The latter are caused for example, by changes in length or by an evening-out of the packing over the circumference of the cylinder. If there is only a frictional connection between the packing and the surface of the spindle acting together with the packing, the packing can move further into the channel without the spindle being displaced in the circumferential direction and therefore turned out of its desired position.